The present invention relates generally to a sensing surface, or focal plane, for an infrared camera. More particularly, the present invention relates to a hybrid focal plane array formed of densely packed Schottky infrared internal emission photodiodes.
In U.S. Pat. No. 3,902,066, issued Aug. 26, 1975 to Roosild et al, there is described a monolithic Schottky barrier array for detecting the infrared portion of the electromagnetic spectrum. Individual Schottky electrodes within the array are connected through enhancement mode field effect transistors to charge coupled devices for providing signals to an infrared vidicon camera. The performance of this array has proven to be limited by aliasing and drop-out effects which are related to the low percentage active area of the array. Space is required within the focal plane for multiplexing the signals derived from the individual Schottky barrier electrodes, and also for the guard rings which are provided about each individual Schottky electrode. In such an array, the charge coupled device signal readout circuitry utilizes up to 50% of the focal plane area. Add to this losses of sensing area because of guard rings and channel stops and the active area of the array is reduced to approximately 30 to 45 percent of the total area of the array.